Abstract
Samples of electrolytic tough pitch copper were deformed in equal channel angular pressing with enhanced productivity to quickly refine its initial coarse-grained microstructure at room temperature. The evolution in microstructure and changes in a broad range of properties were compared to a sample in the undeformed state. The microstructure evolution was evaluated using electron backscatter diffraction for both states and transmission electron microscopy for a detailed microstructure characterization of the deformed sample. The microstructure observations were correlated with the results of tensile tests, electrochemical tests in 3.5 wt% NaCl, electrical conductivity measurements and thermal stability up to 200 °C. The ECAP process employed in this study caused a grain refinement from about 16 µm to about 600 nm. The microstructure refinement caused a 50% increase in both the YS and UTS. The elongation to failure, due to the high amount of LAGBs, maintained a high value of 13.3%. The corrosion and pitting potentials were higher for the deformed sample. Furthermore, the grain refinement caused a decrease in electrical conductivity from 100.2% IACS to 93.1% IACS, a drop of 7% IACS. The deformed sample displayed thermal stability up to a temperature of 175 °C, where there was a drop in micro-hardness of more than 10%.
Highlights
Due to its high electrical conductivity, electrolytic tough pitch (ETP) copper is mainly used in industry for constructing electrical equipment and for electrical installations
The CV factor for both planes shows a high value—above 1, which indicates that the structure has a considerable variety of grain sizes
The histograms of misorientation angle distributions (Fig. 4) are similar for both planes, with the highest peak corresponding to the twin boundaries, indicating the recrystallized microstructure
Summary
Due to its high electrical conductivity, electrolytic tough pitch (ETP) copper is mainly used in industry for constructing electrical equipment and for electrical installations. For such applications, in addition to low resistance, the best possible mechanical strength and high corrosion resistance are required. Pure metals often show inadequate mechanical properties, and so, most are hardened by cold metal forming. Strain hardening is known to slightly worsen a metal’s electrical properties [1,2,3,4]. In the case of demanding applications, copper alloys are used.
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